User`s manual

75
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER with CLOSED CAPTION DECODER
and ON-SCREEN DISPLAY CONTROLLER
MITSUBISHI MICROCOMPUTERS
Rev. 1.0
M37281MAH–XXXSP,M37281MFH–XXXSP
M37281MKH–XXXSP,M37281EKSP
The display start position in the vertical direction is determined by
counting the horizontal sync signal (HSYNC). At this time, when VSYNC
and HSYNC are positive polarity (negative polarity), it starts to count
the rising edge (falling edge) of HSYNC signal from after fixed cycle of
rising edge (falling edge) of V
SYNC signal. So interval from rising edge
(falling edge) of V
SYNC signal to rising edge (falling edge) of HSYNC
signal needs enough time (2 machine cycles or more) for avoiding
jitter. The polarity of HSYNC and VSYNC signals can select with the
I/O polarity control register (address 021716).
Fig. 8.11.9 Supplement Explanation for Display Position
When bits 0 and 1 of the I/O polarity control register
(address 0217
16) are set to “1” (negative polarity)
V
SYNC signal input
V
SYNC control
signal in
microcomputer
0.25 to 0.50 [µs]
(
at f
(
XIN
)
= 8MHz
)
(Note 2)
Not count
12345
Notes 1 : The vertical position is determined by counting falling edge of
H
SYNC signal after rising edge of VSYNC control signal in the
microcomputer.
2:Do not generate falling edge of H
SYNC signal near rising edge
of V
SYNC control signal in microcomputer to avoid jitter.
3:The pulse width of V
SYNC and HSYNC needs 8 machine cycles
or more.
8 machine c
y
cles or more
8 machine cycles
or more
HSYNC
signal input
Period of counting
H
SYNC signal